experiments/csharp/E053-InverseSqrtBenchmarks/Program.cs

36 lines
933 B
C#

using System.Runtime.CompilerServices;
using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Running;
BenchmarkRunner.Run<InverseSqrtBenchmarks>();
[SimpleJob, MemoryDiagnoser(false)]
public class InverseSqrtBenchmarks
{
[Benchmark]
[Arguments(16.0f)]
public float OneOverMathFSqrt(float number)
{
return 1.0f / MathF.Sqrt(number);
}
[Benchmark]
[Arguments(16.0f)]
public float Q_rsqrt(float number)
{
int i;
float x2, y;
const float threehalfs = 1.5F;
x2 = number * 0.5F;
y = number;
i = Unsafe.As<float, int>(ref y); // evil floating point bit level hacking
i = 0x5f3759df - (i >> 1); // what the fuck?
y = Unsafe.As<int, float>(ref i);
y = y * (threehalfs - (x2 * y * y)); // 1st iteration
// y = y * ( threehalfs - ( x2 * y * y ) ); // 2nd iteration, this can be removed
return y;
}
}